Disclosed herein are imaging members, and more specifically, single and multi-layered photoconductive imaging members with a hole blocking or undercoat layer (UCL), a photogenerating layer, a charge transport layer containing a component with a low dielectric constant, such as from about equal to or less than about 2.5, and more specifically, a dielectric constant of from about 1 to about 2.5, and yet more specifically, from about 1.5 to about 2.3.
More specifically, the charge transport layer of the imaging members of the present disclosure are comprised of a polymeric component with a low dielectric constant, examples of this component being poly(phenylene ether) (PPE), poly(cyclo olefin) (PCO), polyesters, polyamides, fluorinated polymers, and polyolefins with no ring structures present on the main polymeric chain, and charge transport molecules. The weight ratio of the polymer and charge transport molecules can be, for example, from about 30/70 to about 80/20. The low dielectric polymer in embodiments possesses a glass transition temperature of from about 80° C. to about 260° C. (degrees Centigrade throughout). Specific examples of PPE polymers are VESTORAN 1900™, a poly-2,6-dimethyl-1,4-phenylene ether polymer, available from Degussa, (temperature of deflection at 0.45 MPa load equal to 185° C. as determined with the known ASTM D648 testing method, and a dielectric constant equal to 2 as determined with the known ASTM D150 at 1 MHz testing method), NORPEX AX290 PPE™, available from Ebbtide Polymers Corporation (temperature of deflection at 1.8 MPa equal to 143° C. as determined with the known ASTM D648 testing method, and a dielectric constant equal to 2 as determined with the known ASTM D150 at 1 MHz testing method). Specific examples of poly(cyclo olefin) polymers include ZEONOR 1600™, a polydicyclopentadiene polymer, available from Zeon Corporation (glass transition temperature equal to 163° C. as determined by DSC; dielectric constant equal to 2.3 as determined with ASTM D150 at 1 MHz), and ZEONEX E48R™, a polydicyclopentadiene polymer, available from Zeon Corporation (glass transition temperature equal to 140° C. as determined by DSC; dielectric constant equal to 2.3 as determined with the ASTM D150 at 1 MHz testing method). Examples of polyesters include EASTAR AN004™, a poly(cyclohexylenedimethylene terephthalate) copolyester, available from Eastman Chemical (temperature of deflection at 0.45 MPa load equal to 103° C. as determined with the ASTM D648 testing method; dielectric constant equal to 2.1 as determined with the ASTM D150 at 1 MHz testing method); examples of polyamides include VESTAMIDE L1940™, a Nylon 12, available from Creanova Inc. (temperature of deflection at 0.45 MPa load equal to 110° C. as determined with the ASTM D648 testing method; dielectric constant equal to 2 as determined with the ASTM D150 at 1 MHz testing method); examples of fluorinated polymers include DuPont 4100 FEP™, a fluorinated ethylene propylene polymer (melting temperature equal to 259° C.; dielectric constant equal to 2 as determined with the ASTM D150 at 1 MHz testing method); examples of polyolefins with no ring structures on the main polymeric chain include VESTYRON 325™, a polystyrene, available from Creanova Inc. (glass transition temperature equal to 89° C. as determined with DSC; dielectric constant equal to 2 as determined with ASTM D150 at 1 MHz testing method), and NOVOLEN 1102J™, a polypropylene, available from BASF (Viscat softening temperature equal to 92° C.; dielectric constant equal to 2.3 as determined with the ASTM D150 at 1 MHz testing method). The thickness of the charge transport layer in embodiments can be, for example, from about 5 microns to about 60 microns, more specifically from about 10 microns to about 40 microns, and yet more specifically from about 15 microns to about 30 microns.
In embodiments the hole blocking layer in contact with the supporting substrate can be situated between the supporting substrate and the photogenerating layer, which is comprised, for example, of the photogenerating pigments of U.S. Pat. No. 5,482,811, the disclosure of which is totally incorporated herein by reference, especially Type V hydroxygallium phthalocyanine, and generally metal free phthalocyanines, metal phthalocyanines, perylenes, titanyl phthalocyanines, selenium, selenium alloys, azo pigments, squaraines, and the like. The imaging members of the present disclosure in embodiments exhibit excellent cyclic/environmental stability, significantly improved BCR wear resistance and substantially no adverse changes in their performance over extended time periods since, for example, the imaging members comprise a mechanically robust and solvent resistant hole blocking layer, enabling the coating of a subsequent photogenerating layer thereon without structural damage. The photoresponsive, or photoconductive imaging members can be negatively charged when the photogenerating layers are situated between the hole transport layer and the hole blocking layer deposited on the substrate.
Processes of imaging, especially xerographic imaging and printing, including digital, are also encompassed by the present disclosure. More specifically, the layered photoconductive imaging members of the present disclosure can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein charged latent images are rendered visible with toner compositions of an appropriate charge polarity. The imaging members are in embodiments sensitive in the wavelength region of, for example, from about 500 to about 900 nanometers, and in particular from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source. Moreover, the imaging members of this invention are useful in color xerographic applications, particularly high-speed color copying and printing processes.